DateTime conversion and comparison in SQL Query

Question

I have a sql query for pulling a report from a table. The idea is to pull the sum of counts, grouped by day of the week, in the local timezone. Dates in the table are stored in UTC.

SELECT (SUM(t.di1) + SUM(t.di2) + SUM(t.di3) + SUM(t.di4)) AS [ScanCount],
       DATEPART(WEEKDAY, t.LocalTime) AS [weekday]
FROM (SELECT di1,
             di2,
             di3,
             di4,
             CreatedOnUTC AT TIME ZONE 'UTC' AT TIME ZONE 'Pacific Standard Time' AS LocalTime
      FROM tableName
      WHERE DeviceId = 649754) t
WHERE t.LocalTime > '03/16/2020 00:00'
  AND t.LocalTime < '03/16/2020 23:59:59'
GROUP BY DATEPART(WEEKDAY, t.LocalTime)
ORDER BY DATEPART(WEEKDAY, t.LocalTime);

A query like this should only return a single day of the week count, but it returns 2 days. This obviously has something to do with the difference in time zones, whereas the UTC time contains dates from both 3/15 and 3/16. It seems that the conversion from UTC to Pacific Time works in the output but the UTC values are used in the where clause. How can I do this comparison to the new converted datetimes and not to the original UTC times?

Answer 1

Comparison between datetimeoffset and string literal works in UTC.
Simplest solution will be to convert datetimeoffset to datetime2. Modify your inner query to:

cast(CreatedOnUTC AT TIME ZONE 'UTC' AT TIME ZONE 'Pacific Standard Time' as datetime2(0)) AS LocalTime